Solid ink or phase change ink printers conventionally receive ink in a solid form, either as pellets or as ink sticks. The solid ink pellets or ink sticks are typically inserted through an insertion opening of an ink loader for the printer, and the ink sticks are pushed or slid along the feed channel by a feed mechanism and/or gravity toward a heater plate in the heater assembly. The heater plate melts the solid ink impinging on the plate into a liquid that is delivered to a print head for jetting onto a recording medium.
One difficulty faced in solid ink technology is differentiation and identification of ink sticks to ensure the correct loading and compatibility of an ink stick with the imaging device in which it is used. Provisions have been made to ensure that an ink stick is correctly loaded into the intended feed channel and to ensure that the ink stick is compatible with that printer. One such provision is directed toward physically excluding wrong colored or incompatible ink sticks from being inserted into the feed channels of the printer. For example, the correct loading of ink sticks has been accomplished by incorporating keying, alignment and orientation features into the exterior surface of an ink stick. These features are protuberances or indentations that are located in different positions on an ink stick. Corresponding keys or guide elements in the ink loader of the phase change ink printer exclude ink sticks which do not have the appropriate perimeter key elements while ensuring that the ink stick is properly aligned and oriented in the feed channel.
World markets with various pricing and color table preferences, however, have created a situation where multiple ink types may exist in the market simultaneously with nearly identical size/shape ink and/or ink packaging. Thus, ink sticks may appear to be substantially the same but, in fact, may be intended for different phase change printing systems due to factors such as, for example, market pricing or color table. Due to the broad range of possible ink stick configurations, marketing strategies, pricing, etc., differentiating the inks sticks so only appropriate ink is accepted by a printer requires methods of identification that go beyond physical keying.